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Give the vertex for the quadratic function: f (x) = (x – 3) (x + 7)​

1 Answer

5 votes

Answer:


Vertex = (-2,-25)

Explanation:

Given


f(x) = (x - 3)(x + 7)

Required

The vertex


f(x) = (x - 3)(x + 7)

Open bracket


f(x) = x^2 -3x+7x-21


f(x) = x^2 +4x-21

Express -21 as 4 - 25


f(x) = x^2 +4x+4-25

Group as:


f(x) = (x^2 +4x+4)-25

Factorize the expression in bracket


f(x) = (x+2)^2-25

The vertex form is:


f(x) = a(x - h)^2 + k

Where the vertex is:


Vertex = (h,k)


Vertex = (-2,-25)

User RoyalSwish
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